WEBVTT Kind: captions; Language: en 00:00:09.001 --> 00:00:14.001 Speed and still more speed. The breathtaking speed of the past is 00:00:14.001 --> 00:00:16.000 just poking along today. 00:00:17.000 --> 00:00:22.000 Faster trains, faster trucks and motor cars speed up the work and play of the 00:00:22.000 --> 00:00:27.001 world. Each increase in speed follows the winning of a skirmish with 00:00:27.001 --> 00:00:30.000 speed's greatest enemy, friction. 00:00:31.000 --> 00:00:37.000 And yet, strange as it might seem, speed is limited to our ability to stop and 00:00:37.000 --> 00:00:43.000 stopping depends upon friction. What a paradox. Do away with friction for more 00:00:43.000 --> 00:00:50.000 speed and yet for more speed add friction. Whether you travel on a 00:00:50.000 --> 00:00:57.000 bicycle, a wagon or the fastest planes or cars, friction protects 00:00:57.000 --> 00:01:03.001 you and your safety depends upon brakes which apply friction for stopping. 00:01:04.001 --> 00:01:10.000 In modern busy traffic, on congested city streets, on the crowded highway or in 00:01:10.000 --> 00:01:15.001 speeding along on the straight open stretches, the safety of men, women and 00:01:15.001 --> 00:01:22.000 children depends upon brakes. No better example of dependable brakes can 00:01:22.000 --> 00:01:26.001 be found than those manufactured by the Chevrolet Motor Company. 00:01:27.001 --> 00:01:33.000 This is the Chevrolet wheel and brake. Notice how smoothly the wheel comes to a 00:01:33.000 --> 00:01:37.000 stop with the slightest pressure on the pedal and how quickly the wheel stops 00:01:37.000 --> 00:01:39.000 when a sharp pressure is applied. 00:01:39.001 --> 00:01:44.001 Before we can appreciate the degree of perfection Chevrolet has reached in its 00:01:44.001 --> 00:01:50.001 brakes, we must understand how friction is used, what its habits are and what 00:01:50.001 --> 00:01:57.001 must be done to take full advantage of it. This 00:01:57.001 --> 00:02:04.000 is a motor car wheel and to this wheel is fastened a brake drum, the part 00:02:04.000 --> 00:02:10.001 to which friction will be applied for stopping. Since friction produces heat, the 00:02:10.001 --> 00:02:16.001 material used for applying friction must resist heat. If it doesn't, it will 00:02:16.001 --> 00:02:22.000 smoke, char, burn and quickly wear out. 00:02:25.000 --> 00:02:30.001 Chevrolet with every available brake material to choose from through exhaustive 00:02:30.001 --> 00:02:37.000 tests has selected the very best for Chevrolet brakes. But regardless of 00:02:37.000 --> 00:02:42.001 the quality of the material, the way this material is used is more important. For 00:02:42.001 --> 00:02:47.001 example, the amount of braking material in contact with the brake drum largely 00:02:47.001 --> 00:02:54.000 determines how long the material will last and how effective and safe the brakes 00:02:54.000 --> 00:03:00.000 are. Look at this, this motor car wheel is spinning and the brake drum turning 00:03:00.000 --> 00:03:05.001 with it. A short brake shoe covered with brake material will be used to stop this 00:03:05.001 --> 00:03:12.000 wheel. Now watch, see how hot the brake shoe gets and how quickly the brake 00:03:12.000 --> 00:03:18.001 material is ground away? The brake shoe is lengthened, the brake shoe doesn't get 00:03:18.001 --> 00:03:22.000 so hot and the brake material lasts longer. 00:03:30.000 --> 00:03:36.001 A still longer and now almost half of the drum is covered with friction 00:03:36.001 --> 00:03:42.000 producing brake material and the wheel is brought to a stop with very little heat 00:03:42.000 --> 00:03:48.001 or wear. It is a simple matter to see that the effectiveness of brakes and their 00:03:48.001 --> 00:03:55.000 durability depend to a large extent upon the amount of braking material in 00:03:55.000 --> 00:04:00.000 contact with the revolving brake drum and the amount of braking material in 00:04:00.000 --> 00:04:05.001 contact with the brake drum not only depends upon the length and number of the 00:04:05.001 --> 00:04:12.000 shoes but upon the diameter and the width of the brake drum. Imagine 00:04:12.000 --> 00:04:18.001 a Chevrolet brake without articulated brake shoes, a brake which from all outward 00:04:18.001 --> 00:04:24.000 appearances applies plenty of brake material to the brake drum. But notice this, 00:04:24.001 --> 00:04:31.000 the ends of the brake shoes are fastened to fixed pivots. Watch as they move 00:04:31.000 --> 00:04:36.000 about these fixed points that the end of the shoe moves farther than the part 00:04:36.000 --> 00:04:42.000 near the pivot. As long as the surface of the brake forms a perfect circle and as 00:04:42.000 --> 00:04:47.000 long as the pivot is located in exactly the right place then all the brake 00:04:47.000 --> 00:04:54.000 material will contact the brake drum. But you can't use the brakes without making 00:04:54.000 --> 00:05:00.001 heat and heat changes the shape of the brake shoe. See this shoe doesn't fit the 00:05:00.001 --> 00:05:05.001 drum anymore, the rigid pivot won't let it so only part of the brake material 00:05:05.001 --> 00:05:12.000 contacts the brake drum and the part that does wears down first. When the brake 00:05:12.000 --> 00:05:18.000 shoe cools off then here's what you get. Now only the ends of the brake shoes 00:05:18.000 --> 00:05:22.001 touch the drum and only parts of the braking material are in contact with the 00:05:22.001 --> 00:05:29.000 drum. This is a Chevrolet wheel and its large brake drum 12 inches in diameter. 00:05:31.000 --> 00:05:36.001 These are Chevrolet brake shoes. Notice how long they are, how much of the inside 00:05:36.001 --> 00:05:42.000 surface of the brake drum they cover. But even more important notice how these 00:05:42.000 --> 00:05:48.000 shoes are supported. Instead of a single pivot for each shoe, each shoe swings on 00:05:48.000 --> 00:05:53.001 a link with two pivots each. Notice too that each shoe can move as it wants to 00:05:53.001 --> 00:05:58.000 and should within the circle of the brake drum. There is nothing to prevent each 00:05:58.000 --> 00:06:03.000 shoe from exactly fitting the brake drum whether it's hot or cold. Now notice 00:06:03.000 --> 00:06:08.000 that this simple little piece as it turns spreads the outer ends of the shoes 00:06:08.000 --> 00:06:14.001 apart. As the brake operates every square inch of braking material hugs the brake 00:06:14.001 --> 00:06:21.000 drum. Every square inch of braking material wears exactly the same. This 00:06:21.000 --> 00:06:27.000 is one of the reasons why Chevrolet brakes work so easily, so effectively and 00:06:27.000 --> 00:06:32.000 they stay in adjustment over thousands and thousands of miles of the hardest 00:06:32.000 --> 00:06:37.001 driving through the heaviest traffic and through any kind of weather. Regardless 00:06:37.001 --> 00:06:44.000 of how well a brake is designed, its moving parts must be protected from water, 00:06:44.001 --> 00:06:51.001 slush, mud, dirt, sand, dust, and grit. If they aren't, they 00:06:51.001 --> 00:06:58.001 can't stand up. This is why Chevrolet protects the interior of its brakes 00:06:58.001 --> 00:07:04.001 with this close-fitting shield and in addition protects the bearing parts against 00:07:04.001 --> 00:07:11.000 rust by plating them with experienced engineers in General 00:07:11.000 --> 00:07:16.001 Motors Laboratories and the Chevrolet Engineering Department, Chevrolet has its 00:07:16.001 --> 00:07:23.000 choice of every available means for connecting brake pedals with brakes. After 00:07:23.000 --> 00:07:29.001 all, why should there be a problem in connecting four mechanical brakes with one 00:07:29.001 --> 00:07:35.001 foot operated pedal? Simplicity is always a thing to be solved, particularly 00:07:35.001 --> 00:07:42.001 where safety is at stake. So Chevrolet with four strong 00:07:42.001 --> 00:07:49.000 steel rods and four strong steel cables through a strong sturdy cross 00:07:49.000 --> 00:07:55.001 shaft and link connected its four mechanical brakes mechanically with the foot 00:07:55.001 --> 00:08:02.001 operated pedal. What could be simpler? What could be safer? A 300 pound man 00:08:02.001 --> 00:08:07.001 standing on a Chevrolet brake pedal could not even spring a single part in the 00:08:07.001 --> 00:08:12.001 entire brake system and the reason is simple, the steel cables are of the same 00:08:12.001 --> 00:08:18.000 material used to lift heavy freight elevators for operating steam shovels and for 00:08:18.000 --> 00:08:24.000 supporting suspension bridges. In fact, here's an entire Chevrolet car hanging on 00:08:24.000 --> 00:08:30.001 just one of Chevrolet's brake control cables. Chevrolet's brake rods 00:08:30.001 --> 00:08:37.000 have a tensile strength of over 3,000 pounds and the cross shaft and link 00:08:37.000 --> 00:08:43.001 is many times stronger than required. Is it any wonder that Chevrolet owners 00:08:43.001 --> 00:08:48.001 speed along without any thought of brakes? The heaviest of traffic doesn't faze 00:08:48.001 --> 00:08:54.001 them for they know from experience that they're cable controlled. All mechanical 00:08:54.001 --> 00:09:01.000 brakes are on the job every instant ready for any emergency at the slightest push 00:09:01.000 --> 00:09:07.000 on the foot pedal smooth safe brakes that stay in adjustment for thousands of 00:09:07.000 --> 00:09:13.001 miles of safe travel and all of this due to Chevrolet engineers 00:09:13.001 --> 00:09:19.001 knowledge of friction the enemy of speed and yet the 00:09:19.001 --> 00:09:21.001 friend of speed.